Re: CHAT: Telling time (wasRe: The English/French counting system (WAS: number systems fromconlangs))

On Mon, Sep 15, 2003 at 09:33:46PM -0400, Isidora Zamora wrote:
> The JulianCalendar lags 13 days behind the Gregorian Calendar due to
> the leap year issue.
Yup, the discrepancy has been 13 days since March 1st/14th, 1900, and
will remain so until March 1st/15th 2100, when it'll go to 14 days.
(It didn't get any worse in 2000 because 2000 was a leap year in both
calendars.)

> When I was a Latin student, I was told that the
> length of a Roman hour varied seasonally...sort of like built-in Daylight
> Savings Time, I guess...more organic, though.
Traditionally, the daytime and nighttime were independently divided up
into 12 "hours" that were only equal within a given half-day.  These
seasonal hours are the ones shown on the sundial, and are still used
for religious purposes by Jews and Muslims.   It was only when mechanical
clocks started to replace sundials that we got a standard hour as 1/24 of
the whole day (measured noon to noon)..

> Your sugestion of a leap week every 5 or 6 years, may have just provided me
> with the solution to a con-calendar problem of my own.
Actually, there have been many combined lunar/solar calendars, and they
all keep things in synch by periodic introduction of leap months.
The Jewish calendar uses a complicated arithmetic system, whereas the
Chinese calendar uses astronomical observation.  (By way of analogy:
if instead of using either the Julian or Gregorian system of leap years
we just made sure that the Spring Equinox was always on March 20 by
inserting a February 29th whenever the equinox threatened to fall on the 21st
instead, that would be an astronomical calendar.  More accurate to the
seasons, but a heck of a lot harder to calculate in advance; that's
the Chinese system).

One ancient solution is the so-called Metonic cycle, which is named
after the Greek Meton but was known to many ancient peoples long
before him: 19 solar years is almost exactly 235 lunar months.
The normal lunar year is 12 months (about 354 days), so 19 of
them is 19 x 12 = 228 months.  That's 7 months short of 19 solar
years, so you need to insert 7 extra months into every 19 years.
(The calculation of Easter is also based on the Metonic cycle).
So if, for instance, the 3rd, 6th, 9th, 11th, 14th, 17th, and 19th
out of every 19 years has 13 months instead of 12, you'll be pretty
close to in synch with the solar year.

-Mark